Hitherto, an industrial endoscope has been used to image an inner side wall surface (hereinafter, referred to as a hole wall surface) of a hole-like inspection subject (hereinafter, referred to as an inspection hole) to inspect whether or not a defect is present on the hole wall surface. In order to conduct the inspection, an insert shaft which is long and thin and is disposed with a wide angle lens at the top end thereof is inserted into the inspection hole. In the inspection, if an adhered substance such as a water drop, a chip, a foreign substance or the like adheres to the lens or the hole wall surface, it is impossible to inspect accurately whether or not a defect or the like is present from a picture imaged by the endoscope.
Thereupon, there has been disclosed in Japanese Patent Laid-open No. H08-050207 a fiberscope attached with a cleaning mechanism which is configured to blow air to a top end surface of a fiber cable to clean a foreign substance adhered to the top end surface. In the fiberscope, a flexible pipe is disposed to cover the outer circumferential surface of the fiber cable so as to form an air passage between the inner circumferential surface of the flexible pipe and the outer circumferential surface of the fiber cable, and a top end portion of the flexible pipe is bent inward to form an air injection portion.